evolutionistPronunciation: /iːvəˈluːʃ(ə)nɪst, -ˈljuː-, ɛ-/Definition of evolutionist noun a person who believes in the theories of evolution and natural selection. adjective relating to the theories of evolution and natural selection:an evolutionist modelDerivatives evolutionism noun evolutionist in other Oxford dictionaries Definition of evolutionist in the US English dictionary